Abstract

Reaction solution circulation and control of heavy by-products are two crucial problems of the caprolactam industry with the consideration of energy conservation. To this end, the Beckmann rearrangement of cyclohexanone oxime, which was catalyzed by a mixed-acid catalyst containing trifluoroacetic acid (TFA) and oleum, was conducted in a microchemical system. The effects of experimental parameters on the heavy by-product, octahydrophenazine (OHP), were assessed, including the molar ratio of TFA to oleum (T/A ratio), molar ratio of oleum to oxime (A/O ratio), SO3 mass fraction, temperature, and TFA distribution between two fluids (D(TFA)). The content of OHP was decreased with the increase of the A/O ratio, T/A ratio, and SO3 mass fraction and a suitable D(TFA) and temperature within the range of experiments. Meanwhile, the adiabatic operation was found favorable and an ultra-low content (<1.0 ppm) of OHP was realized under the optimum conditions. Besides, potential reaction pathways of OHP formation were also proposed and discussed based on the experimental evidence. These results are therefore expected to contribute to the process design and optimization for the industrial production of CPL.

Authors contributing to RSC publications (journal articles, books or book chapters)
do not need to formally request permission to reproduce material contained in this
article provided that the correct acknowledgement is given with the reproduced material.

Reproduced material should be attributed as follows:

For reproduction of material from NJC:
Reproduced from Ref. XX with permission from the Centre National de la Recherche
Scientifique (CNRS) and The Royal Society of Chemistry.

For reproduction of material from PCCP:
Reproduced from Ref. XX with permission from the PCCP Owner Societies.

For reproduction of material from PPS:
Reproduced from Ref. XX with permission from the European Society for Photobiology,
the European Photochemistry Association, and The Royal Society of Chemistry.

For reproduction of material from all other RSC journals and books:
Reproduced from Ref. XX with permission from The Royal Society of Chemistry.

If the material has been adapted instead of reproduced from the original RSC publication
"Reproduced from" can be substituted with "Adapted from".

In all cases the Ref. XX is the XXth reference in the list of references.

If you are the author of this article you do not need to formally request permission
to reproduce figures, diagrams etc. contained in this article in third party publications
or in a thesis or dissertation provided that the correct acknowledgement is given
with the reproduced material.

Reproduced material should be attributed as follows:

For reproduction of material from NJC:
[Original citation] - Reproduced by permission of The Royal Society of Chemistry (RSC) on behalf of the
Centre National de la Recherche Scientifique (CNRS) and the RSC

For reproduction of material from PCCP:
[Original citation] - Reproduced by permission of the PCCP Owner Societies

For reproduction of material from PPS:
[Original citation] - Reproduced by permission of The Royal Society of Chemistry (RSC) on behalf of the
European Society for Photobiology, the European Photochemistry Association, and
RSC

For reproduction of material from all other RSC journals:
[Original citation] - Reproduced by permission of The Royal Society of Chemistry

If you are the author of this article you still need to obtain permission to reproduce
the whole article in a third party publication with the exception of reproduction
of the whole article in a thesis or dissertation.

Information about reproducing material from RSC articles with different licences
is available on our Permission Requests page.